This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Geoffrey Clark, PI Specific Aim 1: Investigation of the RASSF family of Ras effectors in transformation The Ras oncogene has been implicated as a key player in the development of more than a third of human cancers. Ras appears to function by activating multiple, heterologous effector proteins that regulate synergistic signaling pathways controlling growth and development. Experimentally, excess Ras activation leads to vigorous transformation and the best characterized Ras effector proteins are themselves oncoproteins. However, excessive activation of Ras can also cause cells to undergo growth arrest and apoptosis. This suggests that Ras proteins may activate a sub-set of effectors that, rather than promoting transformation, mediate growth inhibition. It would seem reasonable to suppose that such effector systems would have to be subverted during the transformation process to allow progression to tumorigenicity. Specific Aim 2: Development of novel small molecule inhibitors of Ras action Ras has been identified as a prime candidate for targeted anti-cancer therapy for more than two decades, but attempts to develop specific inhibitors of Ras have so far proved ineffective. The best known attempt involved a series of Farnesyl transferase inhibitors that actually do work well on H-Ras but are ineffective against the most important member of the family, K-Ras. Recent work has shown that the most important Ras effector for transformation in human systems is the RalGDS group of effectors. This contrasts with results in murine systems which have implicated Rafs as the key effectors. No inhibitors of RalGDS function have been described.